Method, system and computer program product for managing the transmission of information packets in a telecommunication network

ABSTRACT

To manage the transmission of information packets on channels of a telecommunications network, the packets are organised into user queues received in respective buffers, measuring the occupancy level of the buffers. The users are sorted into respective classes (RT, NRT) identified by the service mode requested. After determining the propagation conditions on the transmission channel respectively associated to said users, the priority in the transmission of the packets is determined, choosing the order in which the respective queues are visited as a function of: —a first level priority, linked to whether the users belong to the respective classes of service (RT, NRT), —a second level priority, linked to at least a parameter chosen between the level of occupancy of the respective buffer and the propagation conditions of the respective channel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US national phase of PCT applicationPCT/EP2003/012551 filed 11 Nov. 2003 with a claim to the priority ofItalian patent application TO2002A001009 itself filed 20 Nov. 2002.

FIELD OF THE INVENTION

The present invention relates to techniques for managing thetransmission of information packets in a telecommunication network.

The invention was developed with particular focus on its possibleapplication to the Packet Scheduling function in Radio ResourceManagement (RRM) in a mobile communication network, such as a networkoperating according to the standard called Universal MobileTelecommunications System or UMTS.

For the sake of illustration simplicity, in the remainder of the presentdescription nearly constant reference shall be made to this possiblefield of application. However, it will be appreciated that the scope ofthe invention is wholly general and hence not limited to said specificapplication context.

By way of general foreword to the description of the prior art, of theproblems constituting the basis for the invention and of the solutionproposed herein, it is useful to summarise some essentialcharacteristics of the technical context into which the invention fits.

In the radio access network of the UMTS system, based on the WCDMA (WideBand Code Division Multiple Access) radio interface, it is essential tooptimise transmitted power in order to maintain interference levels aslow as possible. It is fundamentally important to manage radio resourcesin such a way as to provide quality of services (QoS) and to assure anefficient exploitation of the resources made available by the system.

In essence, starting from the load at the uplink and downlink level, onecan define different states of the network and correspondingly definesuitable management strategies.

The functional block diagram of FIG. 1 shows in general terms the RadioResource Management (RRM) architecture in the application contextdescribed above.

The functions and acronyms shown in the figures are to be consideredwholly known to those versed in the art and hence such as not to requirea detailed description herein.

This holds true in particular for the functions identified by themodules S-RNC (Serving Radio Network controller), C-RNC (ControllingRadio Network Controller), Node B and UE and the interfaces Iur, Iub andUu interposed between them.

The functional blocks shown in FIG. 1 are the following:

-   -   Packet Management (PM),    -   Transport Channel Type Switching (TCTS),    -   Packet Scheduling (PS),    -   Radio Access Bearer (RAB) Management (RABM),    -   Admission Control (AC),    -   Congestion Control (CC),    -   Common Measurements (CM),    -   Dedicated Measurements (DM),    -   Cell Sel/Resel Evaluation (CSRE), and    -   Inter/Intra Frequency Measurements (IIFM).

As stated, the radio resource management (RRM) architecture shown inFIG. 1 corresponds to general operating criteria which are wholly knownin the art and hence such as not to require a detailed descriptionherein, beyond the terms set out hereafter.

In any case, the procedures comprising the architecture of FIG. 1 areillustrated in detail in:

-   -   Harri Holma and Antti Toskala, “WCDMA for UMTS: radio access for        third generation mobile communications”, Wiley/& Sons Ltd 2001”,        and    -   3GPP TR 25.922 V3.7.0 (2002-03) Technical Report 3rd Generation        Partnership Project; Technical Specification Group Radio Access        Network; Radio resource management strategies.

The algorithms that regulate the operation of the management entitiesdescribed above can co-operate for the best management of resources. Thegreater co-operation and interoperability, the more efficient themanagement mechanism, exploitation of available power and resourceutilisation. The 3GPP standard does not specify the way in which suchrelationships can maximise system performance

The UMTS system has the ability to offer a great number of value addedservices. In this scenario, packet switched services play an importantrole, constantly on the rise in the field of cellular communications.The application of data services to cellular systems requirestransferring one or more packets through radio links. Packet switchedservices in the UMTS standard are characterised by connections betweenthe network and mobile users through the set-up of appropriate channels,whose type depends on the type of service.

DESCRIPTION OF THE PRIOR ART

As stated, the UMTS standard does not specify any packet schedulingstrategy.

In general, current proposals for packet scheduling focus on only one ofthe following three points:

-   -   compliance with Quality of Service (QoS) requirements, for        instance in terms of delay and minimum allowed speed;    -   throughput maximisation;    -   total exploitation of available power.

The volume “Radio Network Planning and Optimisation” by J. Laiho et al.,John Wiley & Sons, Ltd., 2001 describes a solution for allocatingcapacity to packet switched (PS) users in a radio network. Inparticular, after the allocation of a new PS user, the load is estimatedto determine whether there is still any available capacity, or whether,on the contrary, the maximum load threshold has been exceeded and thusit is necessary either to proceed with re-dimensioning or to releaseresources.

The same document describes two types of scheduling, one based on codedivision, which tends to let multiple users transmit simultaneously,assigning low transmission speeds to them, and the other one based ontime division, which tends to let one user transmit at a time. However,this way of operating does not allow to optimise the exploitation ofavailable transmissive resources.

The document U.S. Pat. No. 6,374,117 discloses a method and a system forcontrolling a level of transmission power based on the queuing delay ofthe packets within a data transmission radio system. Following thisapproach, throughput in the transmission of data packets can be improvedfor certain connections with reference to queuing delay: in practice,the data packets that were subjected to a considerable queuing delay areallocated a higher quality connection by increasing their transmissionpower. The choice of whether to give priority to given packets or not byincreasing transmission power can be made, for instance, according to auser's quality of service profile. According to this manner ofproceeding, when the delay starts to increase, power is increased toimprove quality. However, this intervention is susceptible to havenegative effects in terms of interference.

In “A scheme for throughput maximization in a dual class CDMA System” byS. Ramakrishna and J. M. Holtzman, IEEE Journal on Selected Areas inCommunications, Volume 16; issue 6, Aug. 1998, pp. 830-844, a study ispresented which demonstrates the validity of a CDMA scheme which uses anuplink packet scheduling algorithm distinguishing between two classes ofpriority or of users, i.e. “delay-tolerant” users and “delay-intolerant”users. The foremost object of the proposed procedure is throughputmaximisation alone, neglecting the other aspects considered above.

The goal pursued by the scheduling procedure proposed in “A QoS OrientedBandwidth Scheduling Scheme on 3G WCDMA Air Interface” by D. Tian, J.Zhu; 2001 International Conference on Info-tech and Info-net, 2001Proceedings ICII 2001—Beijing; Volume 2, pp. 139-144 is resourceallocation based on distinguishing users into Priority classes, thusfocusing on quality of service requirements. No attention, instead, ispaid to the problem of optimisation in the allocation of the resourcesavailable to the cell.

In “Resource Allocation and Scheduling Schemes for WCDMA Downlinks” byR. Vannithamby, E. S. Sousa; IEEE International Conference onCommunications, 2001; ICC 2001, Volume 5; pp. 1406-1410 a study ispresented whose main goal is downlink resource allocation based on thepower assigned to each individual mobile at the base station. Said poweris the critical parameter whereon rate allocation to users is based.However, the problem of throughput maximisation and delay minimisationis not considered.

OBJECTS AND SUMMARY OF THE INVENTION

The object of the present invention is to provide a solution formanaging packets in a telecommunication network, such as to overcome theabove described intrinsic drawbacks of prior art solutions.

According to the present invention, said object is achieved thanks towhat is specifically set out in the claims that follow.

In particular, it will be appreciated that the present invention is tobe described in terms of method, as well as in terms of system, as wellas in terms of computer product able to be directly loaded into thememory of at least a digital computer and susceptible of carrying outthe steps of a method according to the invention when the computerproduct is executed on the digital computer.

In addition to being integrated correctly within the radio resourcemanagement (RRM) architecture, paying particular attention to theprotocols prescribed by the radio layers of mobile communicationnetworks (such as those operating according to the UMTS standard), thesolution for managing packet transmission, described herein, allows tointegrate Packet Scheduling (PS) algorithms and Transport Channel TypeSwitching (TCTS) algorithms, paying the utmost attention to anarticulated set of requirements rather than to individual requirements.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The invention shall now be described, purely by way of non limitingexample, with reference to the accompanying drawings, in which:

FIG. 1, relating to the radio resource management architecture in apacket mobile network and in itself relating both to the prior art andto the solution according to the invention, has already been describedpreviously and it shall be further described hereafter,

FIG. 2 shows the possible variation in the capacity occupied by theusers of a cell of a mobile communication system as a function of time,

FIG. 3 shows an example of determination of the order of visitation ofthe queues in a solution according to the invention,

FIG. 4 is a state diagram describing a procedure susceptible to beimplemented within the present invention, and

FIGS. 5 and 6 show, again in the same application context of theinvention, situations in which a volume of traffic exceeds an absoluteupper threshold or drops below an absolute lower threshold.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

With reference to the function diagram of FIG. 1, the main purpose ofthe Packet Management function PM is to optimise packet transmission onthe radio interface of the related system (deemed to be wholly known).

In general, in the application context of FIG. 1, it is possible tospecify the measurements made in Nodes B and reported to the C-RNC bymeans of the N-Bap protocol, via Iub interface.

The measurements are:

-   -   RTWP (Received Total Wideband Power), defined as the power        received over the entire band, including the noise generated by        the receiver within the band defined by the reception filter.    -   Transmitted carrier power: it is defined as the ratio between        total transmitted power and maximum power in transmission.

Depending on the values of these measurements, at least three differentoperative states can be defined:

-   -   normal operation, which occurs when the following two conditions        are simultaneously met:    -   (RTWP/Thermal Noise Power)<=70% of the maximum Noise_Rise on the        uplink;    -   Transmitted Carrier Power <=70%;    -   operation in alert conditions, which occurs when at least one of        the following two conditions is met (respectively for uplink and        downlink):    -   70% of the maximum Noise_Rise on the uplink<=(RTWP/Thermal Noise        Power)<=90% of the maximum Noise_Rise on the uplink;    -   70%<=Transmitted Carrier Power<=90%    -   pre-congestion operation, which occurs when at least one of the        following two conditions is met (respectively for uplink and        downlink):    -   90% of the maximum Noise_Rise on the uplink<=(RTWP/Thermal Noise        Power)<=maximum Noise_Rise on the uplink;    -   90%<=Transmitted Carrier Power <=100%.

The above definitions are the current ones, well known to those versedin the art. It will also be appreciated that the values of 70% and 90%shown above are provided purely by way of example and can be modified bythe operator.

The table that follows refers to various classes of services susceptibleto be managed in a context such as a UMTS context.

Traffic Class Conversational Streaming Interactive Class Class ClassBackground (Conversational (RT (Interactive Background RT) Streaming)best-effort) (best-effort) Example voice, video facsimile Web BrowsingBackground of (NT) email Appli- audio and downloading cation videostreaming

These services exhibit different characteristics in terms of Quality ofService or QoS.

The essential characteristics of conversational class services are givenby the need to preserve certain time relationships between theinformation entities of the stream and to assure compliance with amaximum delay value.

In the case of streaming class services, it is necessary to maintain thetime relationships between various information entities of the streambut, in general, delay requirements are less pressing than forconversational class services.

In the case of interactive class services, usually oriented to a generalrequest-response configuration, an essential requirement is to preservethe information content or payload.

In the case of background services, requirements are even lessstringent, since, though the requirement of preserving payload contentremains, the recipient generally has no particular expectations in termsof delivery time.

In general terms, it is clear that the Packet Management function PM isable to exploit the fact, within the scope of packet services, it isnecessary in any case to assure a low error percentages on data whilst,at least for some services, a certain quantity of delay can betolerated.

Moreover, some services of the interactive or background class (asdefined in a 3GPP UMTS context), such as the Web browsing service or theelectronic mail service, are essentially best-effort services, for whichno specific bit-rate level is guaranteed.

From this point of view, the delay tolerance characteristics and thebest-effort nature of some of these services can be used with a certaindegree of flexibility to reduce interference and correspondinglyoptimise capacity.

As shown in FIG. 1, the packet management function PM in turn is dividedinto two main functional entities, i.e.:

-   -   packet scheduling or PS, and    -   transport channel type switching or TCTS.

The main function served by packet scheduling is to manage thetransmission of the packets of the supported services on the DCH links(dedicated channel), in order to optimise the radio interface.

The main purpose of the transport channel type switching is to monitorthe transmission characteristics of each connection provided by thepacket scheduling function, in order selectively to command thetransition from the shared channel to a dedicated channel or vice versa.

The packet management module PM manages downlink packet scheduling: thesignificant parameters, which set a limit to the availability of systemresources, are therefore the following:

-   -   maximum power which the base station can deliver;    -   lack of perfect orthogonality between the codes assigned to the        users; and    -   interference from other cells, perceived by UE receivers.

The PM module manages and optimises the totality of the packettransmission, both relating to the services which require thetransmission of long and infrequent packets (Web browsing) and relatingto services such as electronic mail, ftp in which a large quantity oflong packets is transmitted for a short time interval, as well asservices in which few, short packets are sufficient (chat, SMS).

The related functions reside, from an architectural viewpoint, in theServing-RRM, together with the TCTS module and to the RABM module.

The RRM is called “serving” because it represents the set of managementprocedures located within the serving-RNC(S-RNC). This positioningenables it to have available all information about users registered inthe Nodes-B belonging to the RNC, and to the type of radio connectionrequired by them and set up in the network.

Preferably, the scheduling procedure within the PM module that managesthe transmission on the dedicated DCH channel acts as described belowwhen the load situation of the network, according to the definitionsprovided above, is that of normal operation.

In the currently preferred embodiment, for its decisions the procedureuses:

-   -   traffic information about the number of active RT (real time)        connection and their bit rate and signal/interference ratio        (SIR) ratio pursued as a target or SIR_(target);    -   information about the data connections on dedicated channels        which are set up and their characteristics of bit rate,        SIR_(target) and type of service requested;    -   information on the Transport Formats or TF associated to each        data connection on dedicated channel; and    -   occupancy of the buffers of the RLC (Radio Link Control) layer        in terms of quantity of bytes still to be transmitted.

The standard, as can be learned from the specification 3GPP-25.322Technical Specification Group Radio Access Network; Radio Link Control(RLC) protocol specification (Release 1999), provides, as accessprotocols terminated in the Serving RNC, for DCH channels, the followinglayers:

-   -   L1 (physical),    -   MAC (Medium Access Control)    -   RLC (Radio Link Control), and    -   RRC (Radio Resource Control), only control plane.

The example of RRM architecture illustrated herein employs the protocolsprovided by the standard to implement its strategies.

The first three types of information are thus directly available withinthe Serving-RNC; on the other hand, in regard to the knowledge of thequantity to be transmitted, through an appropriate interwork betweenRLC, MAC and RRC, the occupancy values of the buffers of the RLC layer(buffer occupancy) can be made available to the MAC level and hence(through interwork between the two layers) to the RRC layer in which thedecision-making part of the scheduling procedure resides.

The main steps of the procedure described herein are essentially three:

-   -   Estimating residual capacity;    -   Determining priorities;    -   Assigning resources.

The procedure resides, in terms of residual capacity calculation andpriority determination (first two items), at the RRC layer in theserving-RRM.

As will be explained hereafter, resource assignment evaluates the rateto be assigned to each user and consequently assigns the transportformat, i.e. how many transport blocks to withdraw from the buffer ateach transmission interval or TTI. This function always resides in theserving RRM.

The PS module pursues, among its various objectives, that of resourceusage optimisation, assuring an efficient use of the complete capacityof the cell. The PS module must be able, through the knowledge of thecharacteristics of the services supported in the cell and of the numberof active users, to calculate the residual capacity left available bythe real time services, which are assigned the maximum priority,residual capacity left available by packet switching.

To estimate the aforesaid residual capacity, several prior art solutionscan be employed. All this taking into account that, the more accuratesaid estimate, the better will be the results achievable when allocatingresidual capacity.

By way of example, said residual capacity can be determined noting thatfor a given service to be supported correctly, the followingrelationship must be satisfied:

${\lbrack \frac{E_{b}}{N_{0}} \rbrack j},{k = {{{\frac{W}{r_{j,k}}\frac{P_{j,k}h_{j,k}}{I_{{int},k} + I_{{ext},k} + {\eta_{0}W}}} \geq {\gamma_{j}\mspace{65mu} j}} = {1\mspace{14mu}\ldots\mspace{14mu} N}}}$

-   -   where:    -   W is chip rate, for instance equal to 3.84 Mchip/sec;    -   P_(jk) is the power allocated for each individual user j in the        cell K;    -   r_(jk) is the bit rate of user j in the cell k,    -   I_(int,k) is the intracell interference of the cell k,    -   I_(exit,k) is intercell interference;    -   η₀ is the thermal noise spectral density;    -   y_(j) is L′E_(b)/N₀ target to support the service requested by        the user j;    -   h_(jk) is path loss.

Since the scheduling technique illustrated herein focuses on thetransmission on the downlink path, the description that follows shallfocus on said path.

The downlink load of the cell can be expressed as:

$\eta_{DL} = {\sum\limits_{i = 1}^{N}\;{\frac{1}{1 + \frac{w}{r_{j,k}\gamma_{i}}}( {( {1 - \alpha_{i}} ) + f_{i}} )}}$

where f is the ratio between intercell interference and intracellinterference, measured at the receiver of every user equipment or UE andα_(i) is the orthogonality factor, a parameter that takes into accountthe perfect orthogonality between the codes assigned to the N users.

The formula can be simplified considering an average value of α_(i) andof f:

$\overset{\_}{\eta_{DL}} = {\sum\limits_{i = 1}^{N}\;{\frac{1}{1 + \frac{W}{r_{i,k}\gamma_{i}}}( {( {1 - \overset{\_}{\alpha}} ) + \overset{\_}{f}} )}}$

The module PS is organised and acts according to a discrete timestructure based on scheduling time Ts. The time Ts paces the repetitionof all the calculations and the actions of the procedure.

The procedure calculates, for each scheduling time Ts the capacity whichcan be used for packet services.

The maximum load is a threshold determined by the operator and itdefines the maximum downlink capacity η_(DL, max) in the normaloperating state:

$C_{TCS} = \lbrack {\eta_{{DL},\max} - {\sum\limits_{i = 1}^{N_{RT}}\;{\frac{1}{1 + \frac{W}{r_{i,k}\gamma_{i}}}( {( {1 - \overset{\_}{\alpha}} ) + \overset{\_}{f}} )}}} \rbrack$

For each new user who requests a packet service, a respective buffer isallocated for packet transmission, at the RLC layer. The module PS actson the basis of the characteristics of each user's buffer.

It is assumed that the function AC allows the entry into the system ofinteractive or background packet users, by evaluating exclusively thatthey can transmit at the minimum rate prescribed according to the set oftransport formats (8 Kbit/s) and by not instead considering the peakrate negotiated with the network. It is not necessary to prevent suchusers from entering the system; the module PS will assure that theytransmit without congesting the radio interface, checking and settingthe rate of the dedicated connection on a case by case basis, in ordernot to exceed the limits imposed by the characteristics of thetransmission on the downlink path, limits which were listed above.

At this point, setting the value of limit capacity, i.e. of residualcapacity the base station can offer, based on the parameters listed atthe start of the paragraph, it is possible to know which portion ofresource can be allocated for packet users.

When assigning resources, a first distinction made by the module PS—as afirst level or implicit priority criterion—is the one between:

-   -   real time (RT) users: these require conversational or streaming        services (“RT packet” services or users);    -   non real time (NRT) users: these require interactive or        background services (“NRT packet” services or users).

With reference to FIG. 2, it is apparent that the module PS tries toadapt the transmission of packet users to the dynamic variations ofresidual available capacity.

Obviously, this can take place with a discrete timing. The calculationsare repeated at each step, called T_(s) which represents the time thatelapses between an application of the procedure and the subsequent one.It is therefore presumed, with a reasonable degree of approximation if acorrect value is chosen for the T_(s) parameter, that the RT load doesnot change between a step and the subsequent one. The smaller T_(s), themore dynamic and adaptive the application of the scheduling to thesystem will be.

The calculation of priorities, which consists of selecting the orderwherein the queues containing the user packets will be visited, is basedessentially on three criteria:

-   -   a) a first level priority criterion, linked, as stated, to the        belonging to the classes “RT packet” or “NRT packet”: hence,        this is an implicit priority, linked to the nature of the        information conveyed by the packets;    -   b) two second level priority criteria, relating to the operating        dynamics of the system, linked respectively:    -   b1) to the occupancy of the RLC layer buffers, and    -   b2) to the propagation conditions of the channel.

The above criteria are applied observing first the belonging to the twoclasses of service.

In the currently preferred embodiment of the invention, a furtherdistinction is made between those who belong to the same class ofservice according to the greater occupancy of the buffers, i.e. causingthe selection or extraction, among the users with the same first levelpriority, of the user who has higher buffer occupancy.

For equal buffer occupancy, the user who demonstrates best channelpropagation conditions is extracted in view of transmission.

Naturally, at least under particular conditions of use, the second levelpriority criteria described above can be applied in complementaryfashion, or exchanging one for another.

In this case, still observing in the first place the belonging to thetwo classes of service, a distinction is made between those belonging tothe same class of service according to the propagation conditions of thechannel. Among users with the same first level priority, the userdemonstrating the best channel propagation conditions is thus selectedor extracted.

For equal channel propagation conditions, the user with the greatestbuffer occupancy is extracted, in view of transmission.

The occupation of the buffer at the RLC layer can easily be determinedby evaluating, for example, the number of bytes present in the buffer.

Channel propagation conditions can instead be determined in terms ofsignal/interference ratio (SIR), for instance as a function part of ameasurement (SIR_Error) defined as the difference between the measuredvalue (SIR_(measured)) and the target value (SIR_(target)) of thesignal/interference ratio.

FIG. 3 shows an example of how the queue visiting order is calculated.

After assuring that residual capacity is exploited in the best possiblefashion, in order to allocate all available power to the base station,and determining the order of visitation of the queues which obtain thedata packets, the procedure must apply its resource allocation policy,i.e. it must decide as to allocate available capacity in an optimisedmanner, maximising total throughput and minimising user delay.

In practice, after performing its calculation on how to subdividecapacity among data users, the packet scheduling module calculates themaximum transport format TF employable for the particular user andcommunicates it via the transport format set or TFS to the MAC layer,which will use this information in the selection of the transport formatto each TTI. Moreover, if this becomes necessary, the transmission canbe suspended or resumed through the suspend and resume procedure,respectively.

The procedure tries to assign to the highest priority user the transportformat corresponding to the negotiated peak rate. If it fails, it triesto allocate the immediately lower format, continuing with its attemptsuntil the allocated rate falls within the quantity of capacityavailable.

In most cases, it may occur that, after allowing the top priority userto transmit with the maximum rate, some capacity is still available inthe cell. Since the primary task of the module PS is to optimise datatransmission, preventing capacity wastage, the procedure implemented forthe top priority user is repeated, for the next highest priority user,until there are no more resources or active users.

FIG. 4 shows the diagram that describes the states characterising thedownlink transmission to a mobile terminal.

The base station—relative to the data connection of that given mobileterminal—is in the Idle state (100) until the related buffer startsfilling with packets.

The change in state, from “Idle” to “Data to be Transmitted” (102) takesplace when the need to set up a radio channel for the user is verified,since the buffer has started to fill with packets. It is important thatthe system reacts quickly to the changes that occur, to prevent theaccumulation of excessive delay in the buffer.

Permanence in this state is linked to resource availability. At eachscheduling step T_(s), the assessment is made as to whether a datachannel can be assigned to the mobile in question; if the capacityavailable to the cell is sufficient, a Radio Access Bearer (RAB) is setup, so a radio link is created between the BS and the mobile and DataTransmission can begin. Permanence in this state (104) continues as longas there are resources to allocate to the mobile.

When resources are no longer available, the procedure does not order theradio link to be dropped but could invoke, for instance, a procedureprescribed by the standard: CRLC-Suspend (Control RLC).

The mobile will then be in a suspended state (106): hence, it willminimise its occupancy of the radio interface resources, correspondinglyminimising interference, but its connection will remain standing fromthe RLC layer up.

In the suspended state, the RLC entity no longer sends to the underlyingMAC level—or receives in the opposite direction—any PDUs (Protocol DataUnits) with a higher sequence number than the one indicated by thesuspend primitive. Once the resume primitive is recalled, the RLC levelwill re-start transmitting PDUs from the point where it has suspended.

The TCTS module monitors the transmission buffer of each individualpacket connection to understand whether the type of transport channelallocated to support a certain service is the right one or not.

In general, a packet service can be supported on:

-   -   a shared channel (Random Access Channel or RACH or else Forward        Access Channel or FACH), when the service requires the        transmission of small packets and with low frequency (a typical        example is represented by the transmission of SMS message); or    -   a dedicated channel or DCH when service demands in terms of        minimum required bit-rate are high: for instance, this is the        case of browsing services on fast network and of real time        services.

During the normal operation of the network the need may emerge to adaptthe transmission characteristics dynamically to the imposed changes, forinstance modifying the type of transport channel used.

Causes which may bring about such a type channel switch are, forinstance:

-   -   renegotiation of the service, both uplink and downlink,    -   the congestion control module CC orders to switch all        best-effort channels from dedicated channel to share channel to        solve a congestion situation, and    -   particular propagation conditions.

Service renegotiation is the typical case requiring a transport channeltype switch.

For instance, it is supposed that a user requests a browsing service onfast network and then, during normal operation, continues his/hersession by simply sending SMS messages. In this case, bit-rate demandson the radio channel are substantially reduced, thereby imposingtransport channel switching.

To verify when such a situation emerges, the uplink and downlinktransmission buffers are monitored as a function of specific thresholdsapplied to said buffers.

When traffic volume grows, reaching a certain threshold T1, an eventoccurs (4A) which is reported to the serving RNC.

If an event of this kind, schematically shown in FIG. 5, emerges at theuplink level or at the downlink level, a switch from shared channel todedicated channel can be ordered.

If, on the contrary, traffic volume drops below a reference thresholdT2, an event 4B takes place which is also reported to the serving RNC.

This situation is represented in FIG. 6. If said event occurs either atthe uplink level or at the downlink level, a switch can be produced fromdedicated channel to shared channel.

Naturally, when a switch from shared channel to dedicated channeloccurs, a new access step is required along with the allocation of thededicated channel.

In this case, behaviour corresponds to the typical behaviour of theaccess control module AC and of the Radio Access Bearer Managementmodule or RABM. Hence, there is a strict dependence on network state andload.

In the solution illustrated herein, the threshold level which determinesthe switch from shared channel to dedicated channel and/or vice versacan be varied over time. This fact is highlighted in FIGS. 5 and 6,where different threshold levels T1 and T2 are shown.

The variation of the threshold level in question can take placeaccording to traffic parameters such as, for instance, network state(normal—alarm conditions) or the conditions of the channel.

For instance, when the load (in the normal operating state) is reduced,it is possible to encourage use of the dedicated channel (DCH) assuringbetter performance from the quality of service viewpoint, since nocritical situations emerge from the interference point of view.

On the contrary, when the network operates in the alarm operating state,the threshold is set dynamically to make it more difficult to switch tothe dedicated channel. At the end, when the network has to operate innear-congested state, the threshold is further modified, so thatswitching to the dedicated channel is practically forbidden.

In particularly preferred fashion, it is possible to operate in such away that switching from the dedicated channel to the shared channeltakes place even when propagation conditions are very poor, so thebit-rate can be reduced, for instance below 16 Kbps.

It is thereby possible to reduce a connection when the event designatedas 4A or the event designated as 4B take place, or upon reaching athreshold (which can be set by the operator) that indicates the poorquality of the radio link.

For this purpose, one can for instance use the measurement (SIR_Error)defined as the difference between the measured value (SIR_(measured))and the target value (SIR_(target)) of the signal/interference ratio orSIR.

Naturally, without altering the principle of the invention, theconstruction details and the embodiments may be widely varied from whatis described and illustrated herein, without thereby departing from thescope of the invention. In this perspective, it should be recalled onceagain that, although for the sake of simplicity of illustration thepresent invention makes nearly constant reference to the possibleapplication of the invention to an UMTS context, the scope of theinvention is quite general and hence not limited to said specificcontext of application.

1. A method for managing the transmission of information packets onchannels of a telecommunications network comprising the steps of:arranging said packets into user queues received in respective buffersat a base station, by measuring the occupancy level of said buffers,sorting users into respective real time and non real time classesidentified by service modes requested by said users, measuringpropagation conditions on the transmission channel respectivelyassociated to said users, and determining a priority in the transmissionof said packets, by choosing an order in which said respective queuesare visited as a function of: a first level priority, linked to whethersaid users belong to said respective real time and non real timeclasses, a second level priority, linked to both the occupancy level ofthe respective buffer and the propagation conditions of said respectivechannel.
 2. A method as claimed in claim 1, wherein among the users withthe same first level of priority, the user with the highest bufferoccupancy and the best channel propagation condition is chosen.
 3. Amethod as claimed in claim 1, further comprising the step of dividingsaid users into: at least a first real time class, comprising users whorequire conversational or streaming services, and at least a first nonreal time class, comprising users who require interactive or backgroundservices.
 4. A method as claimed in claim 1, further comprising thesteps of: determining the transmission capacity available for thetransmission of said packets, by identifying a negotiated peaktransmission rate value, trying to assign to the highest priority userthe transport format corresponding to said peak rate, by transmittingthe related queued packets in case of positive outcome of saidassignment, in case of negative outcome of said assignment, trying toallocate to said highest priority user the next highest transportformat, said attempts with lower format being continued until theallocated rate falls within the available capacity.
 5. A method asclaimed in claim 4 wherein, after transmitting the information packetsassociated to said highest priority user, the step of detecting anyavailable residual transmission capacity and the step of repeating theprevious steps for said higher priority user, for the user with the nexthighest priority, until there are no more said transmission resources oractive users.
 6. A method as claimed in claim 1, applied to atransmission network organised in respective cells in which saidtransmission resources are shared with real time services which aregiven top priority, further comprising the step of estimating theresidual capacity of the respective cell left free by said real timeservices available for the transmission of said information packets. 7.A method as claimed in claim 1, further comprising allowing access intothe system, via an access control function, to users with informationpackets to be transmitted; the access being conducted, for at least someof said non real time users by evaluating exclusively the possibilityfor said users to transmit their information packets with the minimumrate prescribed by the set of transport formats of the network.
 8. Amethod as claimed in claim 1 or claim 7, further comprising providing apacket scheduling function, configured to verify that at least some ofsaid non real time users transmit without congesting the radiointerface, by controlling and setting, on a case by case basis, the rateof the respective dedicated connection in order not to exceed a givenlimit imposed by the characteristics of said network.
 9. A method asclaimed in claim 1, further comprising the step of organising thetransmission of said information packets by means of a state machinewhich allows: a first state corresponding to the recognition thatinformation packets are present in at least one of said respectivebuffers, a second state corresponding to the transmission of saidinformation packets by means of corresponding transmission resources,and a suspended state corresponding to the recognition of theunavailability of resources for the transmission of said informationpackets with the conservation of said transmission channel, said statemachine being configured to evolve anew from said third state to saidsecond state without dropping said transmission channel, when saidtransmission resources become available again.
 10. A method for managingthe transmission of information packets on a communication networkorganised in cells, in which said information packets can be selectivelytransmitted, within said cells, both on a shared channel and on adedicated channel, comprising the steps of: transmitting the informationpackets of a determined user on said shared channel or on a respectivededicated channel as a function of a related traffic volume, defining atleast one threshold of traffic level, determining at a serving radionetwork controller a switching of the transmission of the informationpackets of said determined user on said dedicated channel starting fromsaid shared channel when the related traffic level grows reaching saidat least one threshold and determining at said serving radio networkcontroller the switching of the transmission of the information packetsof said determined user on said shared channel starting from saiddedicated channel when said respective traffic volume drops reachingsaid at least one threshold, and selectively varying the level of saidat least one threshold.
 11. A method as claimed in claim 10, furthercomprising the step of: reducing said at least one threshold inconditions of reduced traffic in order to favour the use of saiddedicated channel.
 12. A method as claimed in claim 10, furthercomprising the step of: raising said at least one threshold, making moredifficult the switch to said dedicated channel starting from said sharedchannel, under alarmed operating conditions of said network.
 13. Amethod as claimed in claim 10, further comprising the steps of:detecting a state of approaching congestion of said network; andinhibiting the switching to said dedicated channel starting from saidshared channel under said state of approaching congestion of saidnetwork.
 14. A method as claimed in claim 10, further comprising thesteps of: measuring the propagation conditions on the transmissionchannel respectively associated to said determined user as saiddedicated channel; and determining the switching of the transmission ofthe information packets of said determined user on said shared channelstarting from said dedicated channel in the presence of a degradation ofsaid propagation conditions below a threshold value.
 15. A method asclaimed in claim 14, wherein said switching on said shared channelstarting from said dedicated channel is determined as a function of thesignal/interference ratio.
 16. A method as claimed in claim 15, whereinsaid switching to said shared channel starting from said dedicatedchannel is determined based on the difference between the measured valuedetermined when the measured value and the target value of thesignal/interference ratio reach a selectively determined thresholdvalue.
 17. A system for managing the transmission of information packetson channels of a telecommunications network, comprising: a plurality ofrespective buffers configured to receive said packets in user queues ata base station; said users being sorted into respective real time andnon real time classes identified by the service modes requested by saidusers, detector modules able to measure the propagation conditions onthe transmission channel respectively associated to said users, and amodule for managing packet scheduling configured to determine thepriority in the transmission of said packets, by choosing the order inwhich said respective queues are visited as a function of: a first levelpriority, linked to whether said users belong to said respective realtime and non real time classes, a second level priority, linked to boththe occupancy level of the respective buffer and the propagationconditions of said respective channel.
 18. A system as claimed in claim17, wherein said module for managing packet scheduling is configured tochoose, among the users with the same first level priority, the user whohas the highest buffer occupancy and demonstrates the best channelpropagation conditions.
 19. A system as claimed in claim 17, whereinsaid module for managing packet scheduling is configured to: determinethe transmission capacity available for the transmission of saidpackets, by identifying a negotiation peak transmission rate value, tryto assign to the highest priority user the transport formatcorresponding to said peak rate, by transmitting the related queuedpackets in case of positive outcome of said assignment, in case ofnegative outcome of said assignment, try to allocate to said highestpriority user the next highest transport format, said attempts withlower format being continued until the allocated rate falls withinavailable capacity.
 20. A system as claimed in claim 19, wherein saidmodule for managing packet scheduling is configured to detect, aftertransmitting the information packets associated to said highest priorityuser, any available residual transmission capacity and to repeat theoperations carried out for said highest priority user until there are nomore said transmission capacity or active users.
 21. A system as claimedin claim 17, associated to a transmission network organised inrespective cells having a determined transmission capacity shared withreal time services whereto is assigned the highest priority, whereinsaid module for managing packet scheduling is configured to estimate aresidual capacity of the respective cell left free by said real timeservices available for the transmission of said information packets. 22.A system as claimed in claim 17, further comprising an access controlmodule configured to allow users with information packets to betransmitted to enter the system; the access being conducted, for atleast some of said non real time users by evaluating exclusively thepossibility for said users to transmit their information packets withthe minimum rate prescribed by the set of transport formats of thenetwork.
 23. A system as claimed in claim 17, wherein said module formanaging packet scheduling is configured to verify that at least some ofsaid non real time users transmit without congesting the radiointerface, controlling and setting on a case by case basis the rate ofthe respective dedicated connection in order not to exceed a given limitimposed by the characteristics of said network.
 24. A system as claimedin claim 17, further comprising a state machine which allows: a firststate corresponding to the recognition of the fact that informationpackets are present in at least one of said respective buffers, a secondstate corresponding to the transmission of said information packets bymeans of corresponding transmission resources, and a suspended statecorresponding to the recognition of the unavailability of resources forthe transmission of said information packets with the conservation ofsaid transmission channel, said state machine configured to evolve anewfrom said third state to said second state without dropping saidtransmission channel, when said transmission resources become availableagain.
 25. System for managing the transmission of information packetson a communication network organised in cells, in which said informationpackets can be selectively transmitted, within said cells, both on ashared channel and on a dedicated channel, comprising a module formanaging packet scheduling configured to: transmit the informationpackets of a determined user on said shared channel or on a respectivededicated channel as a function of a related traffic volume, define atleast one threshold of traffic level, determining the switching of thetransmission of the information packets of said determined user on saiddedicated channel starting from said shared channel when the relatedtraffic level grows reaching said at least one threshold and determinethe switching of the transmission of the information packets of saiddetermined user on said shared channel starting from said dedicatedchannel when said respective traffic volume drops reaching said at leastone threshold, wherein said module for managing packet scheduling isconfigured selectively to vary the level of said at least one threshold.26. A system as claimed in claim 25, wherein said module for managingpacket scheduling is configured to reduce said at least one thresholdunder reduced load conditions in order to favour the use of saiddedicated channel.
 27. A system as claimed in claim 25, wherein saidmodule for managing packet scheduling is configured to raise said atleast one threshold, making more difficult the switching towards saiddedicated channel starting from said shared channel under alarmedoperating conditions of said network.
 28. A method as claimed in claim25, wherein said module for managing packet scheduling is made sensitiveto a state of approaching congestion of said network and is configuredto inhibit the switching to said dedicated channel starting from saidshared channel, under said state of approaching congestion of saidnetwork.
 29. A system as claimed in claim 25, further comprising atleast one detector module configured to detect the propagationconditions on the transmission channel respectively associated to saiduser as said dedicated channel and said module for managing packetscheduling is configured to determine the switching of the transmissionof the information packets of said determined user on said sharedchannel starting from said dedicated channel in the presence ofdegradation of said propagation conditions below a threshold value. 30.A system as claimed in claim 29, wherein said module for managing packetscheduling is configured to determine said switching on said sharedchannel starting from said dedicated channel as a function of thesignal/interference ratio detected by said at least one detector module.31. A system as claimed in claim 30, wherein said module for managingpacket scheduling is configured to determine said switching on saidshared channel starting from said dedicated channel based on thedifference between the measured value and the target value of thesignal/interference ratio reaching a selectively determined thresholdvalue.